1. Field of the Invention
The present invention relates to a torque converter, and more particularly to a torque converter provided with a lockup clutch.
2. Background Information
A torque converter includes three types of vane wheels (impeller, turbine and stator) in the interior thereof, and serves to transmit torque by means of a working fluid (working oil) in the interior thereof. The impeller is fixed to a front cover that transmits torque, and an impeller shell and the front cover form a fluid chamber that is filled with the working fluid. The turbine is disposed inside the fluid chamber opposite the impeller. When the impeller rotates, the working fluid flows from the impeller toward the turbine to rotate the turbine. As a result, torque is transmitted from the turbine to a main drive shaft of a transmission.
A lockup clutch is disposed in a space between the front cover and the turbine, and serves to mechanically couple the front cover to the turbine and thereby directly transmit torque therebetween. The lockup clutch is primarily composed of a piston, and an elastic coupling mechanism that serves to couple the piston to the turbine or another output member. The piston is disposed between the front cover and the turbine so as to form a front chamber on the front cover side and a rear chamber on the turbine side. As a result, the piston can move toward and away from the front cover by means of a pressure differential created between the front and rear chambers. A friction facing is provided on the front cover side of the outer peripheral portion of the piston in order to form a frictional coupling portion.
The elastic coupling mechanism is composed of a drive member fixed, for example, to the piston, a driven member fixed to a member on the turbine side, and elastic members such as coil springs disposed between the drive and driven members and capable of torque transmission.
A thrust washer is usually disposed in the axial direction between an inner peripheral portion of the front cover and a turbine hub. The thrust washer functions to support the thrust load of the turbine. In addition, a plurality of grooves are formed in an end surface in the axial direction of the thrust washer that radially extend through the thrust washer so that the working fluid can flow between the front chamber of the torque converter and the oil passage of the main drive shaft via these grooves (see, for example, Japanese Unexamined Patent Application Publication No. H05-231495).
When a conventional thrust washer is provided in a torque converter, the number of parts will increase as well as the overall cost thereof. Costs will increase when a thrust washer is provided because the surface on which the thrust washer slides must be processed to improve the precision thereof.
In view of the above, there exists a need for a hydrodynamic torque transmitting device which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.